2025 Sep 07
#TimeTravelTuesday #ThoughtExperiment: Many #Worldlets?
or in other words, fractions of #World, not the whole World. #TimeTraveler #theories often involve splitting or multiplying #universes. Time Travel events divide #spacetime into two near-identical clones. Grandfather lived or did not, you did not meet yourself or you did. But if we think this through further, its scope might not be quite so universal as typically presented.
Take 3 heavenly bodies: Mother #Earth, the #AlphaCentauri triple star system (at 4+ light years away), and #Polaris, the #NorthStar (at 400+ light years away).
Now we program our #TimeMachine to take us back one year (#retrograde) where we meet ourselves. Hi selves! This all takes place in one year. There's the original us, there's us leaving the present, and there's us meeting our past/original selves a year earlier — standard #boilerplate #scifi #movie #script.
Alpha Centauri will have to wait another 3 years before any of this information can get to there. This is related to the concept of a #lightcone which expands at the speed of light. This doesn't sound quite so much like birthing a twin universe, does it? Now what about the North Star? It will have to wait 433 years for news of our Time Travel event(s). And that's still pretty much in our tiny #celestial neighborhood.
The point is that the effects of such events are largely localized and rapidly diluted as we move farther away. This still has its paradoxical problems, but it doesn't quite feel like the whole universe dividing into two — maybe part of it (a universelet? a subuniverse?) Possibilities are that in moving further out in space-time, the effects of a Time Travel incident may be 'blurred out', as are anomalous numerical samples in the law of large #numbers. If one pours a cup of coffee into a lake, it doesn't change the color of the lake. There is a brief chaotic #glitch before it is no longer measurable.
It is tempting to imagine space-time as "stitching" itself back together. (Glitch & stitch?) Such speculations are related to #StephenHawking's "chronology protection conjecture" of 1992. And along with #blackholes, #entanglement, and other #quantum phenomena, if Time Travel is possible, then we should be looking for it at every scale. We could be surrounded by time-traveling particles everywhere all the #Time.
https://Wikipedia.org/wiki/Many-worlds_interpretation … #ManyWorlds https://Wikipedia.org/wiki/Temporal_paradox#Consistency_paradox … #GrandfatherParadox https://Wikipedia.org/wiki/Light_cone … #LightCone https://Wikipedia.org/wiki/Time_travel#Absence_of_time_travelers_from_the_future … #TimeTravelTheory https://Wikipedia.org/wiki/Law_of_large_numbers … #LawOfLargeNumbers https://Wikipedia.org/wiki/Chronology_protection_conjecture … #ChronologyProtectionConjecture
Sean Carroll, a renowned theoretical physicist and FQxI member spoke at XPANSE recently.
As we gear up to watch his talk, we’re revisiting one of Sean's earlier discussions with FQxI. 
Check it out 
The Many Worlds Interpretation sounds cool, but is it really useful? 
While it explains some quantum weirdness, it's impossible to test and leads to an overwhelming number of parallel realities. Sometimes, less is more! 
